Process for purifying an aryl olefine having the styrene structure as a nucleus



Patented July 1, 1947 PROCESS FOR PURIFYING AN ARYL OLE- FINE HAVING THESTYRENE STRUCTURE AS A N UCLEUS Claude W. Jordan, Paoli, Pa., assignorto The United Gas Improvement Company, a corporation of Pennsylvania NoDrawing. Application October 24, 1944, Serial No. 560,195. In CanadaSeptember 23, 1944 12 Claims. 1

This application is a continuation-in-part of my copending applicationSerial No. 398,403, filed June 17, 1941, and of my copending applicationSerial No. 430,886, filed February 14, 1942, which has matured intoPatent 2,363,676, granted November 28, 1944.

This invention pertains generally to the purification of aryl olefinesand pertains particularly to the purification of aryl olefines obtainedfrom similar boiling point or are capable of forming azeotropic mixtureswith the desired hydrocarbon. This is especially true in the case ofstyrene and methylstyrene, in which the usual polymerizing diificultiesare increased by the pronounced tendency of the material to polymerizeduring the fractionation process. For example, a typical methylstyrenefraction obtained by ordinary distillation processes will contain hardlymore than light oil. lo 50% or 60% methylstyrene.

More specifically, this invention pertains to the This has led to thedevelopment of auxiliary purification of polymerizable aryl olefines bythe methods for increasing the concentration of light application ofamides of metals in group IA and oil methylstyrene fractions and oflight oil group IIA of the periodic table. styrene fractions to thedesired extent.

It is a j c o he present invention o purify Methylstyrene fractions andstyrene fractions aryl olefines by the use of one or more amides ofobtained by the fractionation of light oil accordalkali or alkalineearth metals under carefully ing to the usual methods employed in theart, as controlled conditions. Another object of the inwell as those oflower and higher concentration vention is the provision of certainmethods obtained, for example, by the use of more drastic whereby arylolefines may be purified by the apfractionating methods and/or the useof certain plication of one or more amides of alkali or specialconcentrating methods, are generally alkaline earth metals Without undueloss of aryl suited for the manufacture of synthetic resins by olefinein the form of aryl olefine polymers of low suitable polymerizationmethods, except that the q yresulting resins are very often too inferiorwith Other objects of the invention will be apparent respect to color,color stability, electrical resistto those skilled in the art from aninspection of ance, molding properties, freedom from crazing, thefollowing description and claims. thermal stability, melting point,specific viscosity,

This invention is particularly adapted for the molecular weight, andmechanical strength as to purification of aryl olefines containing the eof any considerable value. styrene structure as a nucleus, such asstyrene; I find that these deficiencies are generally alkylstyrenes,particularly alkylstyrene in which traceable to the presence of certaincontaminatthe alkyl substituents each contain less than 5 ing materialsin the methylstyrene fractions, and carbon atoms such as themethylstyrenes, for in the styrene fractions during the polymerizingexample, the side chain substituted methylprocess. styrenes such asalpha methylstyrenes and beta- While I have not as yet exactlydetermined the methylstyrene and the nuclearly substituted character ofall of these impurities, experimental mono-methylstyrenes such aso-methylstyrene, evidence indicates that they may be classified inIii-methylstyrene, and p-methylstyrene; ethylcertain specific groups.styrene; isopropylstyrene; normal-propylstyrene; For example, a. typicalstyrene fraction ob- -ethylmethylstyrene; methylisopropylstyrene;ditained from light oil Was found to containanmethyl-tertiary-butylstyrene; and the like. proximately 0.1% sulfurand a typical methyl- In the various processes for the manufacturestyrene fraction obtained from light oil was of combustible gas such asoil gas, carburetted analyzed and found to contain appreciable quanwatergas, or coal gas, considerable quantities of titles of sulfur. Thisindicatesthat crude styrene tar are produced, and the gas containssubstanand crude methylstyrene obtained from the tial quantities ofreadily condensible materials. above sources contain a relatively largequantity These condensates, including the light oil obofsulfur-containing materials, such as mercaptained upon distillation ofthe tar, are sources for tans, disulfides, and/ or d at of t OD manyhydrocarbons. In particular, they are and related compounds. sources ofstyrene and methylstyrene. Another portion of each of these fractionswas With ordinary methods of fractional distillatreated with amercurating solution which retion as now practiced, it is impossible toseparate sulted in the production of a copious precipitate. many ofthese unsaturated compounds in a sub- Precipitates obtained fromdifierent portions of stantially pure state because of the presence ofthe starting material varied in color from a faint other materials whichapparently are either of yellow to a light brown. This indicates, amongother things, the presence of substituted thiophene and thiophenehomologues.

The treatment of various light oil fractions with ammoniacal cuprouschloride resulted in the formation of a heavy yellow precipitate. Thisindicates the presence of acetylenic compounds, such as phenylacetyleneand methylphenylacetylene. Further work resulted in the isolation ofsubstantial quantities of phenylacetylene from several light oil styrenefractions, indicating that this material is a principal impurity oflight oil styrene, and also resulted in the isolation of substantialquantities of methylphenylacetylene from several light oil methylstyrenefractions, indicating that this material, as Well as other substitutedacetylenes, such as benzylacetylene is a principal impurity of light oilmethylstyrene.

All of the above mentioned acetylenic compounds are acetylenic compoundshaving a hydrogen atom attached to a carbon atom of a triple bond.

Similar tests made with pure styrene diluted with xylene and with puremethylstyrene diluted with xylene to the same concentration as the crudestyrene fractions and the crude methylstyrene fractions treated abovegave results which were negative in each case.

Indene also is an important impurity of light oil methylstyrenefractions, and imparts particularly undesirable properties to thepolymers derived therefrom.

Other types of impurities are doubtless present also in light oilstyrene fractions and in light oil methylstyrene fractions. Among thesetypes of impurities may be included oxygenated compounds such as organicperoxides; organic per acids; aldehydes, for example, formaldehyde,benzaldehyde and methyl benzaldehyde or mixtures of aldehydes, forexample a mixture of formaldehyde and benzaldehyde; and other reactiveclasses of compounds.

An important class of compounds in light oil styrene fractions and inlight oil methylstyrene fractions, from the standpoint of theirinfluence upon the properties of the polystyrene and polymethylstyrenesubsequently obtained from such fractions, are the colored compoundswhich impart a yellow or yellow-brown color to the said fractions. WhileI have not as yet determined the actual structure of any of thesecolored compounds, certain evidence indicates that they mainly compriseunsaturated compounds with conjugated systems of double bonds.

As indicated above, it is difficult, if not impossible, to prepare acommercial grade of polystyrene or polymethylstyrene from crude lightoil fractions unless at least some of the contaminating impurities areremoved.

While the exact influence of each of these contaminating materials isnot known, it may be pointed out that they may act (1) as accelerators,resulting in the production of polystyrene or polymethylstyrene ofrelatively poor quality under polymerizing conditions which wouldnormally result in the production of a good grade of polystyrene orpolymethylstyrene; (2) as inhibitors, reducing the quantity ofpolystyrene or polymethylstyrene obtained under normal polymerizingconditions, and/or (3) they may take part in the reaction and become anintegral part of the resin molecule.

The presence of contaminating impurities in the polymer moleculeundoubtedly would weaken it, causing the resin to be less stab to he tand to decompose readily with the formation of undesired color bodies.

The highly reactive nature of the styrene and methylstyrene present inlight oil fractions of the type disclosed. makes it extremely difficultto remove the contaminating impurities.

I have found, however, that, by a proper choice of conditions such astemperature, time of contact, method of application, and so forth, theundesired contaminating materials mentioned, including color andcolor-forming compounds, may be removed without a considerable loss ofthe desired hydrocarbon. This is accomplished by the application of oneor more amides of metals'in groups IA and HA of the periodic table,preferably in finely divided form, which term as used herein is intendedto include solutions or dispersions in suitable solvents or vehicles.

Amides of metals in group IA and HA of the periodic table, namely,lithium, sodium, potassium, rubidium, caesium, magnesium, barium,strontium, and calcium, or mixtures containing one or more of thesematerials may be used for refining impure aryl olefine fractions,particularly those obtained from light oil. Due to the availability andlow cost of sodium and potassium, Eh'owever, amides of these metals arepreferred for the use set forth herein.

Examples of amides which may be used to refine aryl olefirres inaccordance with my invention are sodium amide, potassium amide, lithiumamide, magnesium amide, barium amide and the like.

Due consideration must be given to the fact that many of these amidesmay be active catalysts for the polymerization of aryl olefines such asstyrene and methylstyrene. Consequently, great care must be exercised inorder to operate the process within well defined limits in order toeffect the removal of the impurities present without polymerizingexcessive quantities of the monomeric aryl olefine present in the crudefraction treated.

The most important of these reaction variables are (1) degree ofsubdivision of the treating agent, (2) concentration of the aryl olefinefraction treated, (3) quantity of amide used, (4) reaction temperature,(5) quantity and type of impurities present in the aryl olefinefraction, (6) method of applying the amide to the aryl olefine fraction,('7) speed of agitation and (8) reaction time.

In view of the extrem difficulty in exactly delimiting each variable inthe wide variety of possible combinations of the foregoing eightvariables, resort will be had to an expression for reaction conditionswhich Will be well understood by persons skilled in the art uponbecoming familiar with this invention. It; may be said that treatingconditions should be such, having in mind what has been said withrespect to the above variables, as to avoid a substantially largepolymerization of the aryl olefine under treatment. In other words, thearyl olefine such as styrene and methylstyrene is treated under reactionconditions insufilciently severe to polymerize a large part thereofduring treatment.

Once knowing what the variables in treating conditions are and theeffect of such variables, it is relatively simple for the person skilledin the art upon becoming familiar with this inven tion to control hisreaction conditions to avoid unnecessary polymerization of the arylolefine undergoing treatment.

Undoubtedly, the most, important of thes reaction'varia-bles is thedegree of subdivision of the treating agent. As pointed out previously,particularly satisfactory results are obtained when the treating agentis very finely divided or is used in the form of a solution in asuitable solvent. While it is difiicult to assign a definite size abovewhich it may be said that the respective amides are ineflicient, it hasbeen found that when the degree of subdivision is such that the majorportion of the amide is comprised of particles smaller than in eachdiameter, excellent results are obtained.

Almost ny desired method may be employed in the preparation of themetallic amides utilized in the practice of the invention. Particularlyadvantageous results have been obtained in the practice of my inventionwhen utilizing sodium amide prepared by adding ammonia-soluble salts ofiron, nickel or cobalt, for example ferric nitrate, to a solution ofsodium in liquid ammonia at low temperature, for example a temperatureof about 33 C., in the presence of a catalyst such as sodium oxide,sodium peroxide, and mixtures of sodium oxides.

Styrene fractions containing from 1% to 99.9% monomeric styrene may betreated by the method described herein to produce Water-white refinedfractions possessing only traces, or none of yellow color, or undesiredimpurities, such as phenylaoetylene, benzaldehyde and the like.

Methylstyrene fractions containing from 1% to 99.9% monomeric methylstyrene may be treated by the method described herein to producewater-white refined fractions possessing only traces, or none, ofundesired impurities, such as methylphenylacetylene, methylbenzaldehydeand the like. Fractions containing at least styrene or at least 30%methylstyren are preferred, particularly when the monomer is to beconverted into polystyrene or polymethylstyrene. For this purpose, astyrene fraction or a methylstyrene fraction of at least concentrationis particularly preferred.

While th boiling range of extremely dilute styrene fractions may cover afairly wide range, boiling ranges between approximately 30 to 59 C. at20 mm. pressure, to 165 C. at Z60 mm. pressure) and more especiallybetween approximately 36 and 52 C. at 20 mm. pressure and 155 C. at 760mm.) are preferred. Narrower fractions such as between approximately 42and 48 C. at 20 mm. pressure C. and C. at 760 mm.) are particularlydesirable. While the boiling range of extremely dilute methylstyrenefractions may also cover a fairly wide range, boiling ranges betweenapproximately 57 to 72 C. at 20 mm. pressure to 180 C. at 760 mm.pressure) and more especially between approximately 60 and 68 C. at 20mm. pressure and C. at 760 mm. pressure) are preferred. Narrowerfractions such as between approximately 61 and 68 C. at 20 mm. pressure(167 C. and 173 C. at 760 mm. pressure) are particularly desirable.

Extremely dilute fractions may be employed in some instances, such aswhen it is desired to react styrene or methylstyrene with some othercompound, in which case my treatment serves to purify such styrene ormethylstyrene for reaction purposes.

Certain precautions, however, should be observed, particularly in thecase of styrene fractions or methylstyrene fractions containing highconcentrations of monomeric styrene or of monomeric methylstyrene. Asthe styrene or methylstyrene present infractions containing highconcentrations of monomeric styrene or of monomeric methylstyrene mayhave a pronounced tendency to polymerize in the presence of certain ofthe amides such as sodium amide, particularly when such materials are invery finely-divided form, certain precautions with respect to reactiontemperature and time should be observed with such fractions in order toprevent undue polymerization thereof, as will be more particularlydescribed hereinafter.

The desired quantity of sodium amide or other metallic amide for theremoval of undesired impurities from styrene fractions or methylstyrenefractions will vary considerably with the concentration of the fractionand the type and concentration of the impurities present. Thus, infairly dilute fractions 'it will be found that from two to five timesthe theoretical quantity of sodium amid to react with thephenylacetylene or methylphenylacetylene present usually will besufiicient to refine the sample to the desired extent. In the case ofvery concentrated fractions, however, such as those containing 98-99.9%styrene or methylstyrene, this ratio may be increased to 30 or even 80times the quantity required to react with the phenylacetylene or themethylphenylacetylene present,

The reaction temperature may vary from very low temperatures, such as 33C. Which is the boiling point of ammonia and lower up to moderately hightemperatures, such as 60 C. However, a safe upper limit to precludeexcessive polymerization of styrene or of methylstyrene is 50 C., andthis is preferably reduced to 30 C. in the case of, very concentratedstyrene fractions or methylstyrene fractions.

The desired quantity of sodium amide or other active metal amide to beused to refine a given styrene fraction or a given methylstyrenefraction is determined in large measure by the type and quantity ofimpurities present. In most cases, however, the quantity ofphenylacetylene or of methylphenylacetylene found in a given sample maybe taken as a measure of the total impurities present. As pointed outpreviously, the amount of sodium amide to be used may be varied such asfrom two to eighty times the quantity required to remove thephenylacetylen or the methylphenylacetylene, the exact amount preferablyused being dependent largely upon the concentration of styrene ormethylstyrene in the fraction.

The method of applying the active metal amide has a considerableinfluence upon the rapidity with which the impurities are removed. Thus,the use of a dispersion of sodium amide in liquid ammonia such \as asolution of sodium amide or suspensions of colloidal sodium amide inliquid ammonia will be found to almost instantaneously remove theimpurities from a given styrene fraction or a given methylstyrenefraction due to the molecular dimensions of the individual sodium amideparticles and to the intimate contact be-- tween the two phases.

The speed of agitation has a very profound bearing upon the rate ofremoval of impurities from styrene or methylstyrene. In general, it maybe said that the rate of removal of such impurities varies directly withthe speed of agitation employed.

The time of reaction is an important variable in the removal ofimpurities from styrene or methylstyrene. As pointed out previously,many of the treating agents described may be good catalysts for thepolymerization of monomeric styrene and of monomeric methyl-styrene.Consequently, care should be exercised not to exceed certain definitereaction periods in :order to prevent any undue loss of styrene ormethylstyrene :in the form of polystyrene or polymethylstyrene.

Generally speaking, it may be said that the time of reaction may varyfrom a few seconds to several hours, depending mainly upon theconcentration of the styrene fraction or methylstyrene fraction beingtreated and the reaction temperature. Thus, with very dilute styrenefractions or -met-hylstyrene fractions, say 30-50% concentration, andrelatively low reaction temperatures, say 25 C., a reaction time of fromthree to seven hours normally may be employed without undue loss ofstyrene or methylstyrene.

With highly concentrated styrene fractions or -methylstyrene fractions,say from98 to 99.9%

concentration, and fairly low reaction temperatures, say from toC.,'reaction times ranging from several seconds to one hour may beemployed.

An increase in the reaction temperature employed in the foregoingillustrations is preferably met with a corresponding reduction in thereaction time in order to prevent excessive polymerization.

The following examples will serve to illustrate my invention.

Example I A 0.1 gram portion of metallic sodium was added to amechanically stirred mixture of 0.03 gram of powdered ferric nitrate(Fe(NO3) 361-120) in 50 cc. of liquid ammonia in a round bottom flask.Dried air was bubbled through the solution until the blue color wasdischarged. .A 2.5 gram portion of metallic sodium then was added to thereaction mixture in small pieces and the mixture stirred until the bluecolor was completely discharged.

This solution andsuspension of sodium amide .in liquid ammonia was addedto 300 cc. of a crude styrene fraction at a temperature of .33 C. withgood agitation. This crude styrene fraction contained 50.5% styrene and0.38% by weight of phenylacetylene; it had a color of about 42(Gardner). The mixture was agitated for .a period of about 1 hour duringwhich the .liquid ammonia .present was completely volatilized. Thecolorof the styrene fraction changed from yellow to a deep brown, and avoluminous red precipitate was formed.

The reaction product was distilled, whereupon a .cleansparkling producthaving a color of less than 0.3 (Gardner) and containing less than 0.01%phenylacetylene was obtained.

E 130.777.1716 I I A 4.0 gram portion of freshly scraped magnesiumribbon and 2.0 grams of anhydrous sodium iodide were placed in a Pyrexcombustion tube.

The tube was then heated under vacuum to 200 C. for minutes to removetraces of moisture.

Ammonia gas, dried by passage through calcium oxide, was passed into thetube and condcnsed to the liquid state by immersing the tube in a dryice toluene bath cooled to 40 C. Approximately .01 gram of sodiumdissolved in liquid ammonia was added to the contents-of the tube andfaint blue color was imparted to the liquid ammonia phase. The reactingmixture slowly acquired .a deep opaque blue color. The reagents wereallowed to react for 16 hours .at

nesium amide thus prepared and the mixture was subjected to agitation.The crude styrene almost immediately acquired a deep red color and areddish-brown precipitate was deposited.

The reaction product was distilled, whereupon a product having a colorof about 0.3 (Gardner) and containing about 0.12% phenylacetylene wasobtained.

In the specification and in the claims the following terms have thefollowing meanings.

The term a metal of group IA and group IIA of the periodic system isemployed as definitive of the group of metals consisting of lithium,sodium, potassium, rubidium, caesium, magnesium, barium, strontium, andcalcium.

The term alkali metal is employed as definitive of the group of metalsconsisting of lithium, sodium, potassium, rubidium and caesium.

The term alkaline earth metal is employed as definitive of the group ofmetals consistin of magnesium, barium, strontium and calcium.

The term finely divided is intended to mean a material reduced to such astate of fineness that the preponderating part is composed of particleshaving no diameter of greater than p g", as well as materials in thecolloidal or dissolved form.

While reagents and procedures of a particular nature have beenspecifically described, it is to be understood that these are by way ofillustration. Therefore, changes, omissions, additions, substitutions,and/or modifications might be made within the scope of the claimswithout departing from the spirit of the invention.

1 claim:

1. A process for purifying an aryl olefine having the styrene structureas a nucleus contained in a mixture which also contains at least oneacetylenic compound of similar boiling point and having a hydrogen atomattached to a carbon atom of a triple bond and at least one aldehyde ofsimilar boiling point which comprises commingling with said mixture afinely divided amide of a metal selected from the group consisting ofmetals of groups IA and HA of the periodic system under conditionsinsufficiently drastic to polymerize the preponderant part of said arylolefine, and separating said aryl olefine in purified form from theresulting mass.

2. A process for purifying an aryl olefine having the styrene structureas a nucleus contained in a mixture which also contains at least oneacetylenic compound of similar boiling point and having a hydrogen atomattached to a carbon atom of a triple bond which comprises comminglingwith said mixture a finely divided amide of an alkali metal underconditions insufficiently drastic to polymerize the preponderant part ofsaid aryl olefine, and separating said aryl olefine in purified formfrom the resulting mass.

3. A process for purifying an aryl olefine hav- .ing the styrenestructure as a nucleus contained in a mixture which also contains at.least one acetylenic compound of similar boiling point and having ahydrogen atom attached to a carbon atom of a triple bond which comprisescommingling with said mixture a finely divided amide of an alkalineearth metal under conditions insufiiciently drastic to polymerize thepreponderant part of said aryl olefine, and separating said aryl olefinein purified form from the resulting mass.

4. A process for purifying an aryl olefine having the styrene structureas a nucleus contained in a mixture which also contains at least oneacetylenic compound of similar boiling point and having a hydrogen atomattached to a carbon atom of a triple bond which comprises comminglingWith said mixture finely divided sodium amide under conditionsinsufiiciently drastic to polymerize the preponderant part of said arylolefine, and separating said aryl olefine in purified form from theresulting mass.

5. A process for purifying an aryl olefine having the styrene structureas a nucleus contained in a mixture which also contains at least oneacetylenic compound of similar boiling point and having a hydrogen atomattached to a carbon atom of a triple bond which comprises comminglingwith said mixture finely divided potassium amide under conditionsinsufiiciently drastic to polymerize the preponderant part of said arylolefine, and separating said aryl olefine in purified form from theresulting mass.

6. A process for purifying an aryl olefine having the styrene structureas a nucleus contained in a mixture which also contains at least oneacetylenic compound of similar boiling point and having a hydrogen atomattached to a carbon atom of a triple bond which comprises comminglingwith said mixture finely divided magnesium amide under conditionsinsufliciently drastic to polymerize the preponderant part of said arylolefine, and separating said aryl olefine in purified form from theresulting mass.

7. A process for purifying an aryl olefine having the styrene structureas a nucleus contained in a mixture which also contains at least oneacetylenic compound of similar boiling point and having a hydrogen atomattached to a carbon atom of a triple bond which comprises comminglingsaid mixture With a dispersion of sodium amide in liquid ammonia underconditions insuificiently drastic to polymerize the preponderant part ofsaid aryl olefine, and separating said aryl olefine in purified formfrom the resulting mass.

8. A process for purifying styrene contained in a mixture which alsocontains at least one aldehyde of similar boiling point comprisingcommingling with said mixture a finely divided amide of a metal selectedfrom the group consisting of metals of groups IA and HA of the periodicsystem under conditions insuificiently drastic to polymerize thepreponderant part of said styrene, and separating styrene in purifiedform from the resulting mass.

9. A process for purifying methylstyren contained in a mixture whichalso contains at least one aldehyde of similar boiling point comprisingcommingling with said mixture a finely divided amide of a metal selectedfrom the group consisting of metals of groups IA and HA of the periodicsystem under conditions insufficiently drastic to polymerize thepreponderant part of said methylstyrene, and separating methylstyrene inpurified form from the resulting mass.

10. A process for purifying methylstyrene contained in a mixture whichalso contains indene comprising commingling with said mixture a finelydivided amide of a metal selected from the group consisting of metals ofgroups IA and HA of the periodic system under conditions insufi'lcientlydrastic to polymerize the preponderant part of said methylstyrene, andseparating methylstyrene in purified form from the resulting mass.

11. A process for purifying a light oil styrene fraction containingother material of similar boiling point in addition to styrene andincludin phenylacetylene which comprises mixing said fraction with adispersion in liquid ammonia of sodium amide under conditionsinsufiiciently drastic to polymerize the preponderant part of thestyrene contained in said light oil fraction, and separating purifiedstyrene from the resulting mass.

12. A process for purifying a light oil methylstyrene fra-ctioncontaining other material of similar boiling point in addition tomethylstyrene including an acetylene which comprises mixing saidfraction with a dispersion in liquid ammonia of sodium amide underconditions insufliciently drastc to polymerize the preponderant part ofthe methylstyrene contained in said light oil fraction, and separatingpurified methylstyrene from the resulting mass.

CLAUDE W. JORDAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,363,676 Jordan Nov, 28, 19441,541,176 Ostromeslensky June 9, 1925 1,680 070 Schroeter Aug. 7, 1928FOREIGN PATENTS Number Country Date 264,245 Germany Sept. 9, 1913 OTHERREFERENCES Richter, Textbook of Organic Chemistry (1938), John Wiley &Sons, Inc., New York city, pages 47 and 48. (Copy in Div. 31.)

